The effect of financial constraints on the optimal design of public transport services

Recent experience with the design of bus services in Santiago, Chile, seems to confirm Jansson's (1980) assertion regarding observed planned bus frequency and size being too low and too large, respectively. We offer an explanation based upon the relation between cost coverage, pricing and optimal design variables. We recall that average social cost decreases with patronage, which generates an optimal monetary fare below the average operators' cost, inducing an optimal subsidy. Then we compare optimal frequency and bus size—those that minimize total social costs—with those that minimize operators' costs only. We show that an active constraint on operators' expenses is equivalent to diminish the value of users' time in the optimal design problem. Inserting this property back in the optimal pricing scheme, we conclude that a self-financial constraint, if active, always provokes an inferior solution, a smaller frequency and, under some circumstances, larger than optimal buses.

漫漫长路

航运公司正寻求能规避巴拿马运河和苏伊士运河通行费的替代方案。     

Turbulent mixing and internal tides in Gaoping (Kaoping) Submarine Canyon, Taiwan

Turbulent overturning on scales greater than 10 m is observed near the bottom and in mid-depth layers within the Gaoping (formerly spelled Kaoping) Submarine Canyon (KPSC) in southern Taiwan. Bursts of strong turbulence coexist with bursts of strong sediment concentrations in mid-depth layers. The turbulence kinetic energy dissipation rate in some turbulence bursts exceeds 10^− 4 W kg^− 1, and the eddy diffusivity exceeds 10^− 1 m² s^− 1. Within the canyon, the depth averaged turbulence kinetic energy dissipation rate is ~ 7 × 10^− 6 W kg^− 1, and the depth averaged eddy diffusivity is ~ 10^− 2 m² s^− 1. These are more than two orders of magnitude greater than typical values in the open ocean, and are much larger than those found in the Monterey Canyon where the strong turbulent mixing has also been. The interaction of tidal currents with the complex topography in Gaoping Submarine Canyon is presumably responsible for the observed turbulent overturning via shear instability and the breaking of internal tides and internal waves at critical frequencies. Strong 1st-mode internal tides exist in KPSC. The depth averaged internal tidal energy near the canyon mouth is ~ 0.17 m² s^− 2. The depth integrated internal tidal energy flux at the mouth of the canyon is ~ 14 kW m^− 1, propagating along the axis of the canyon toward the canyon head. The internal tidal energy flux in the canyon is 3–7 times greater than that found in Monterey Canyon, presumably due to the more than 10 times larger barotropic tide in the canyon. Simple energy budget calculations conclude that internal tides alone may provide energy sufficient to explain the turbulent mixing estimated within the canyon. Further experiments are needed in order to quantify the seasonal and geographical distributions of internal tides in Gaoping Submarine Canyon and their effects on the sediment flux in the canyon.     

Review of ship slamming loads and responses

The paper presents an overview of studies of slamming on ship structures. This work focuses on the hull slamming, which is one of the most important types of slamming problems to be considered in the ship design process and the assessment of the ship safety. There are three main research aspects related to the hull slamming phenomenon, a) where and how often a slamming event occurs, b) slamming load prediction and c) structural response due to slamming loads. The approaches used in each aspect are reviewed and commented, together with the presentation of some typical results. The methodology, which combines the seakeeping analysis and slamming load prediction, is discussed for the global analysis of the hull slamming of a ship in waves. Some physical phenomena during the slamming event are discussed also. Recommendations for the future research and developments are made.     

Investigation and analysis of high temperature corrosion and degradation of marine boiler combustion swirler

The present paper investigated and analyzed swirler material consisting of mild steel which was subjected to service for the period of one year in a 30 MW marine boiler. Due to the presence of high temperatures in the furnace coupled with the corrosive marine environment swirler material showed accelerated degradation and material wastage. An investigation into the feasibility of manufacturing the existing swirler with an alternate material or coating the swirler material with a thermal barrier coating was undertaken. Based on their properties and performance, SS 304 and SS 316 were proposed as the replacement materials for the swirler. The other alternative of coating the existing swirlers with a form thermal barrier coating to observe for any improvement in their performance at elevated temperatures was also tested. Stellite, which is a Ni-Co based coating, was carried out on the MS samples and the same were exposed to same temperatures mentioned above. The performance of the available options was evaluated with respect to the grain structure of the material, the hardness value of the materials and deterioration at elevated temperatures. Investigation showed the proposed materials/coatings like SS 304, SS 316 and Stellite coating revealed that SS 316 is the material best suited for high temperature application.     

Investigation on the rudder force of a ship in large drifting conditions with the MMG model

Journal of Marine Science and Technology - The rudder force, including interference with a ship hull in large drifting conditions, is investigated in this study by captive model tests using a ship...     

Path planning and collision avoidance for autonomous surface vehicles II: a comparative study of algorithms

Journal of Marine Science and Technology - Artificial intelligence is an enabling technology for autonomous surface vehicles, with methods such as evolutionary algorithms, artificial potential...     

Logistics as a driving force for development under the Belt and Road Initiative – the Chinese model for developing countries

ABSTRACT

An important objective of “the Belt and Road Initiative” is to promote the economic growth of countries in the region. China’s successful development experience, proposed in the initial stage of reform, can be summarised as “Looking for development, building the highway first”. This study is the first to evaluate whether logistics infrastructure has indeed contributed to economic growth by employing an error correction model with panel data from 2003 to 2014. In addition, we compare the influence levels of different sectors of logistics infrastructure in different regions, i.e. developed and developing regions. We focus on developing regions as they represent good development experiences for developing countries in the Silk Road Economic Belt. For developing regions, we find that the most influential factors are telecommunication and airway transportation, which should be the foci of attention in order to promote economic growth and reduce inter-region economic inequalities. The research confirms that logistics is indeed a driving force for economic growth in China, and that the contributions of specific sectors can be a useful reference for developing countries to determine prioritisation of investment in different logistics sectors across regions.